JPS5870866A - Two-tone coating method of automobile body - Google Patents

Abstract

PURPOSE:To perform lap coating without grinding a boundary part between two colors, by using acryl resin and aminoaldehyde resin having specified compositions as two kinds of paint to be used for two-tone coating. CONSTITUTION:The first-color paint comprising acryl resin and aminoaldehyde resin (melamine resin) at the weight ratio of 70:30-65:35 is applied to an undercoat paint-applied surface. Clear paint is applied thereon to form the first-color coat 1b without drying the obtained first-color paint film 1a. After baking, the surface except a boundary part between the first-color paint film and the second- color paint film to be applied in the following step is masked, the second-color paint film 2a is formed without grinding the boundary part, and then clear paint is applied under the condition that the obtained paint film is not dried yet, to form the second-color clear paint film 2b. The part where the two paint films are overlapped has good paint adhesiveness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of painting an automobile body. More specifically, the present invention provides two to tone construction of an automobile body.
ne) In painting, the present invention relates to a painting method that does not require polishing of the first color paint film in the area where the two color paint films overlap.

One way to improve the appearance of automobile bodies is to
Tone painting is used. What is two-scene painting?
Painting the exterior of an automobile body in two or more colors (usually two colors).

The conventional two-tone painting method for automobile bodies is to first apply a first color paint to the entire outer body panel, bake it, and then apply a second color paint to the required areas and bake it. It occupies the mainstream. In this case, the first color paint film is usually baked 2UjjJ, but if you include the baking at the time of repair, it is exposed to a total of three baking times, resulting in overbaking, so it is especially important to apply the second color paint repeatedly. In such areas, problems such as peeling and cracking occur due to poor adhesion between the first color coating and the second color coating. To solve this problem, the first color paint is applied to the necessary parts of the body skin,
After baking, a method is adopted in which a second color of paint is applied to the remaining area;
Some problems remain at the color boundaries. For example, when using metallic color type paint, the first
As shown in the figure, the first color consists of a first color base (Ia) and a clear foot (1b)]l! The overlapped area between the film and the second color coating film consisting of the second color base coat (2m) and clear paint) (2b) is due to the adhesion between the 811 color clear coat (1b) and the second color pace coat. is low.

The causes of decreased adhesion are the following (i) to (iii).

(1) Curing of the first color coating proceeds excessively.

(Kawa) There are adhering obstacles between the layers of the paint film (for example, spray dust, gorge in the air, dirt inside the car body, etc.).

(ili) The compatibility between the first color coating film and the second color coating film is poor.

That is, since different resins are used for the base coat and top coat, there are differences (modulus of elasticity, coefficient of expansion, etc.) between the two layers.

In order to overcome this problem of adhesion, conventionally, a coating film of the first color was formed, and the border area was polished by sandpaper polishing, sand pound polishing, etc., so that the boundary line between the first color and the second color was Mask it with tape to make it clearly visible, then add the second
A method of forming a colored coating film has been adopted. However, it is quite difficult with the current technology to polish only the actual overlapping areas, and in reality, polishing extends beyond the areas where the first color coating is covered with the second color coating (overlapping areas). In order to prevent deterioration of the appearance quality, delamination, and deterioration at the color boundaries of the two-tone paint, after removing the masking tape, it is necessary to perform final polishing with an ultra-fine sand pound. Polishing conditions are imposed.

Similar problems are also seen in metallic color type (first color)-solid color type (second color) and some solid-metallic or solid-solid two-tone coatings.

The present invention was made in view of such conventional problems,
The purpose of the present invention is to provide a two-tone coating method for an automobile body that does not require polishing of the boundary between the first color top coat and has high adhesion in the overlapping area between the first color top coat and the second color top foot. do.

That is, in the present invention, the resin components of the clear paint of the first color coating are an acrylic resin and an aminoaldehyde resin,
After forming a 1111-color paint film on the body side using a paint with a weight ratio of 70:30 to 65:35, a second color paint film was applied to the rest of the body exterior without polishing the boundaries. The present invention also relates to a two-tone painting method for an automobile body, characterized in that the two-tone painting method is applied to an overlapping portion.

The method of improving adhesion by improving the material itself of clear paints has tended to be considered not an effective means because the weather resistance, which is an important property of clear paints, is conventionally lost. However, the parts of an automobile body that are prone to deterioration are concentrated in the horizontal parts of the body skin (such as the hood and roof), which are exposed to sunlight for a long time. In areas that receive relatively little exposure to radiation, there is not much deterioration of the paint film.

Taking this into consideration, for example, as shown in Figure 2, we applied a first color coating with an improved high-adhesion clear layer to the side parts of the body (8) where deterioration is less likely to occur, and then applied a first color coating film with a single layer of improved high-adhesion clear paint to the horizontal parts. It is thought that the above-mentioned problem can be solved by applying a second color coating film having a clear layer with emphasis on weather resistance to the remaining portion (4) including the conventional one.

The clear paint for the first color coating used in the present invention contains an acrylic resin and an aminoaldehyde resin as resin components in a weight ratio of 70:30 to 65:55.

Specifically, the acrylic resin has a composition such as l-butyl methacrylate, 1-butyl methacrylate, t-butyl methacrylate, 2-hydroxypropyl methacrylate, and 2-butyl methacrylate.

Further, as the aminoaldehyde resin, those for general paints can be used, but melamine-formaldehyde resins are preferred from the viewpoint of weather resistance.

Such a clear paint may further contain a surface conditioner, a catalyst for accelerating curing, an anti-repellent agent, an extender pigment, etc., as required. Due to the low content of styrene and styrene yarn monomers, which were added to conventional methods to improve weather resistance, accelerated weather resistance tests (SWOM
As for the weather resistance (test), for example, cracking and peeling occur for about 2000 hours, which is slightly inferior to that of conventional clear paints, but is within an acceptable range for the reasons mentioned above.

On the other hand, when the clear paint used in the present invention was used as the first color clear coat, the adhesion with the second color paint was sufficiently good even without polishing. Although there is no sufficient theoretical basis for this reason, it is probably because the acrylic resin has a slightly larger amount of functional groups such as hydroxyl groups, carbonyl groups, and carboxyl groups.

The clear paint used in the present invention preferably falls within the above range; if the aminoaldehyde resin content is less than the above range, the weather resistance will be significantly reduced, and if it is more than the above range, sufficient adhesion will be ensured. Not only will this become impossible, but the mechanical properties will deteriorate.

Next, the clear paint used in the present invention will be explained in more detail with reference to Examples and Comparative Examples. FIG. 3 is a schematic front view of a two-tone coated plate on which a first color coating film and a second color coating film are formed on a dull steel plate used in the following Examples and Comparative Examples.

Example 1 Liptadiene-based electrodeposition paint was applied to a dry coating film of 20μ on a dull steel plate with a thickness Q of 8mm that had been subjected to zinc phosphate chemical conversion treatment.
It was electrodeposited so that it would look like this, then baked at 170'0 for 20 minutes, and then polished with $4oo Nando paper.

Next, apply the car intermediate coating Cer 7 Acer to a dry coating film of 20
It was coated so as to have a thickness of μ, and then baked at 120°0 for 30 minutes, sanded with water using $400 sandpaper, and drained and dried.

To this material, 200 parts of 50% acrylic resin (superimposed part, the same applies hereinafter), 40 parts of 60% melamine resin, and 0.1 part of pigment are added to 40 parts of toluene, 30 parts of Swazol $1000 (manufactured by Maruzen Sekiyu ■), and 20 parts of butyl acetate. A metallic paint whose viscosity was adjusted in addition to a mixed solvent consisting of 10 parts of black and n-butanol was applied to a film thickness of 15 μm. Clear paint (acrylic resin 1
A resin mixture consisting of 40 parts of melamine resin and 50 parts of melamine resin was heated to a viscosity of 32 seconds (7 ord cup $
The viscosity was adjusted to 4/20°O) and was applied to a film thickness of 25 μm.

The first color coating was baked for 20 minutes at 15,000° C. to obtain a first color coating having a total thickness of 40 .mu.m.

Next, mask the first color coating with masking tape so that an overlapping part (7) of about 85 mm is created.
Next, a metallic paint having the same composition as that used for the first color is applied to the part (6) of the dull steel plate, and while the resulting paint film is not dry, a clear paint (18 parts of dispersed acrylic resin, optional) is applied. A solution consisting of 18 parts of molten acrylic resin, 9 parts of melamine resin, 111!S butanol and 44 parts of ethylcyclohexane) was applied. 140 this thing
Baking was carried out at 0°C for 20 minutes, and finally the masking tape was removed to obtain a two-tone coated dull steel plate.

The initial adhesion of the overlapping parts of the coating film and the 40
When the adhesion resistance was observed with the naked eye after being left in water at °C for 120 hours, all were found to be good.

An accelerated weathering test (SWOM test) was also conducted, and both coatings showed no change at all, indicating good weathering resistance.

Examples 2 and 3 An experiment was conducted in the same manner as in Example 1, except that the clear paint used to form the first color coating was replaced with one having the composition shown in Table 1, and a two-tone coated board was obtained. .

The adhesion and weather resistance between the resulting coating films were tested in the same manner as in Example 1. The results obtained are shown in Table 1.

Table 1 Comparative Example 1 The clear paint used to form the first color coating was dispersed in Acrylic A.
The procedure was carried out in the same manner as in Example 1, except that a conventional clear paint consisting of 18 parts of /resin, 18 parts of soluble acrylic resin, 9 parts of melamine resin, 11 parts of butanol, and 44 parts of ethylcyclohexane was used, and Two Tone was obtained. I got a painted dull steel plate.

The initial adhesion and water-resistant adhesion between the coating films tested in the same manner as in Example 1 were both poor, and peeling occurred between the coating films.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the boundary between the first color coating film and the second color coating film in the two-tone coating according to the present invention. Figure 1g2 is a schematic side view showing an embodiment of applying two-tone paint to an automobile body. FIG. 3 is a schematic front view of a dull steel plate coated with two-tone paint. (Main symbols on the drawing) (1b)! 1st color Clear foot (3): Body side part of the car body (5): 1st color
Color paint film forming part (6): Second color paint film forming part (γ): Overlapping part

Claims (1)

[Claims] 1 The 11 components of the #11 color M film clear paint are acrylic resin and aminoaldehyde resin, and the weight ratio is 70='50 to 65:35, and the first color paint film is applied to the body side. A two-yen painting method for an automobile body, which is characterized in that after forming the second color paint film, the second color paint film is formed on the remaining body outer panels and overlapping parts without polishing the boundary parts.